a) Field of the Invention
The present invention relates generally to a system for the separation of lower density debris from higher density debris, and more particularly to such a system, method and apparatus which is particularly adapted to separate construction debris where the low density fraction in general has a density lower than the density of water, and the high density fraction has a density substantially greater than water. More particularly, this would be particularly adapted for use where a large percentage of the low density fraction comprises wood, and also a large portion of the high density fraction comprises rock, cement, metal and other materials commonly found in building structure or other structures.
b) Background Art
It is common practice that when a building structure is being demolished, the debris is simply gathered somewhat indiscriminately into piles and then carried to the dumpsite. Particularly in more recent years, it has been found to be more economical to simply use bulldozers, back hoes, demolition balls, explosives, etc. Depending upon the building or other structure being demolished, there may be a very high percentage of wood or other low density material, or a relatively small amount of the same.
One of the challenges regarding disposal of construction debris is how to recycle or process this material so that it could be used for some useful purpose, instead of just being accumulated in the dumpsite as waste material. Such debris, if properly sorted and/or processed, could be used for land fill, or road beds and this may be accomplished by crushing the rock or rock like material into smaller particles. However, organic material such as wood, is not desirable for a land fill. First, the organic material would decay over time and thus have its load bearing capability degraded. Second, quite often wood pieces come in sections of a two by four, etc., and when placed in a land fill these could protrude upwardly from the surface, etc.
With regard to the wood component of the construction debris, if properly separated, this could be recycled into a variety of useful products, such as ground cover, fuel, etc.
The practical problems in the existing separating processes are often too expensive relative to the economic return that might be realized by productive use of the separated and/or processed materials. The sheer mass and volume of construction debris generally makes manual separation uneconomical. Attempted separation by machinery, (e.g. back hoes and/or bull dozers) involves not only the expense of operating the machinery, but the separation process itself is difficult to be accomplished effectively.
It has been known for many decades, if not centuries, that the separation of material in accordance with its density could be achieved by flotation techniques, where the liquid medium has a specific gravity between that of the two fractions which are to be separated (i.e. where one of the fractions to be separated has a density greater than the liquid medium and the other density less than this liquid medium). Such flotation techniques have been employed in a wide variety of commercial applications.
Accordingly, it is understandable that there have been attempts to use flotation techniques to separate the low density fraction (which would generally comprise in large part wood and possibly other material having a specific gravity less than water) and the high density fraction (comprising stone, concrete, metal pieces, etc.). To the best knowledge of the applicant, the efforts to effectively accomplish such separation by flotation have only marginal success. One method is to provide an upwardly open tank which is filled with water. The construction debris is deposited into the tank, and two back hoes are operated to remove the separated fractions. One back hoe is used to skim the top of the water to remove the wood particles, while the other back hoe is used to remove the denser particles which fall to the bottom of the tank.
Another method and apparatus is disclosed in two U.S. patents (U.S. Pat. Nos. 5,240,114 and 5,110,454). In both of these patents, there is shown a system where a mixture of rock, soil particles and wood is introduced into a water tank. Near the upper water level, a plurality of jet nozzles direct streams of water through the mixture to remove the lower density particles so that these flow toward a slanted baffle 66, thence over the baffle into an area where some of the wood particles float, and some descend downwardly onto a wood piece conveyor 150. This conveyor removes the wood pieces from the water. The rocks from the mixture drop down onto a rock receiving portion 82 where there is a rock conveyor that removes these from the water tank.
A search of the patent literature has disclosed a number of other patents which relate generally to flotation/separation techniques for variety of industrial environements. These are described below.
U.S. Pat. No. 5,373,946 (Olivier) discloses a separating apparatus which utilizes what is termed a xe2x80x9cscrolledxe2x80x9d barrel. It is pointed out that these are classified as mono- or bi-directional. In the mono-directional barrels both of the floats and sinks move in the same direction and exit in the same end of the barrel. The bi-direction barrels have the floats and sinks move in opposite directions. It is pointed out that in the bi-directional barrel the raw feed is introduced near the place where the sinks are evacuated and the only practical way of evacuating the sinks is by means of a scrolled cone. However, there is a very annoying problem which the patent points out as up to the time of this patent never been solved in a satisfactory way, namely, how to prevent a small percentage of the floats from working their way toward the sink side of the barrel and eventually reporting with the sinks being screwed up to the sinks evacuation cone. This is solved by having the discharge end of the rotating drum formed having a fursto-conical configuration, and the larger diameter input end has a diameter greater than that of the main central barrel. Also, there is a barrier positioned at the front side of the main central portion to prevent the floats from proceeding toward the high density end. Further, the high density discharge portion has its large diameter end of a diameter greater than that of the central portion.
U.S. Pat. No. 5,169,005 (Beane) shows a separator in which material passes into a chamber that is provided with paddle drum 20. The material enters through chute 32, and the lighter material is impelled across the surface of the fluid by additional fluid supplied under pressure through nozzle 16. The lighter material passes out through chute 40. The paddles drum 20, brings up the heavy material that exits through 78.
U.S. Pat. No. 5,104,047 (Simmons) shows a waste treating system in which material entered through hopper 36, and the floating material is driven into a chopping or milling means 34, by fluid injected through jets 62. The heavier accumulates on the bottom and is removed by conveyor 70.
U.S. Pat. No. 4,944,869 (Lyakov et al.) shows a system in which a mix of crushed storage battery material is separated into constituent material by a series of flotation units as shown on sheet 5. The separator unites are formed of rotating flotation unites in which the lighter weight materials pass through, and the heavier materials separate out as them material moves through the system.
U.S. Pat. No. 3,392,828 (Muller) shows a separator in which a mix of materials enters the system via 2, and pass into a fluid fill chamber. There is a rotating mesh drum with vanes 12, operating in the fluid body. The drum is slanted relative the surface of the fluid so that at the input end the fluid is below the entrance, but at the output end the fluid flow out. Small heavy, particles 7 fall through the mesh, while large heavy bodies 9, are lifted by the vanes so as to drop on chute 10, and roll out of the separator. The light material which floats on the fluid passes out on the right below chute 10.
U.S. Pat. No. 3,101,312 (Brinkmann) shows a separator in which the materials to be separated enter through weir 4, and are carried by vanes 10 to the top of the device where the lighter material is carried out through scoop 6, while the heavy material accumulates at the body.
U.S. Pat. No. 2,700,466 (Logue et al.) shows a pair of flotation separators 26, and 27. The material to be separated enters section 26, through chute 50, and falls into fluid body 54, where the fluid carries the floating light material out through discharge chute 62. The heavy materials are raised by fins 42, and passes into section 27. In section 27, the middle weight material floats on the fluid and runs out opening 36a, to chute 89. The heaviest material is carried up through 69, where it passes out through chute 86.
U.S. Pat. No. 2,608,716 (Harris) shows in FIG. 3, a device that separates oyster meat from shell fragments. The meat with shell material are carried by belt 31, to the flotation bath where the meat floats and is propelled by fluids from nozzles 43, toward belt 36. The small fragments fall to belt 44, and are carried off.
U.S. Pat. No. 384,861 (Melkersman) shows a device that separates good grain from bad, as well as other light materials. The materials to be separated enter through xe2x80x9cIxe2x80x9d, and fall into the water. The heavy material moves down to the large end of the rotating cylinder and is lifted by buckets xe2x80x9cGxe2x80x9d, to fall onto screen xe2x80x9cHxe2x80x9d. the light material floats out over the lip of the cylinder into screen xe2x80x9cHxe2x80x9d.
Accordingly it is an object of the present invention to provide a separation system, method and apparatus which is particularly adapted to effectively accomplish the separation of debris into lower and higher density fractions. More particularly, the present invention is particularly adapted to solve the various challenges that are involved in the separation of construction debris, where there is a desirable balance of advantages, such as accomplishing the process efficiently, at reasonable cost, with high production, and reliably.
In the method of the present invention, there is provided a rotatably mounted drum which comprises a surrounding side wall and front and rear end walls having, respectively, front and rear discharge openings. The drum defines a processing chamber with a lower water containing chamber region, having an upper level at an upper water level in the region and a lower level at a lower side wall portion at the region. At least part of the water containing chamber region is positioned at a level below lower portions of the front and rear openings. The drum has a high density debris conveying structure which is arranged to engage high density debris at a lower part of the water containing chamber region. The water containing chamber region is filled with water to form a body of debris processing water in the chamber region.
Then the debris is delivered into the processing chamber at a receiving location at the water containing chamber region.
Additional water is delivered into the processing chamber at a water discharge location forward of the debris receiving location. This additional water is delivered at a location adjacent to the upper level of the water containing region in a rearward direction generally aligned with the upper level of body of water at a sufficiently high velocity into an upper high velocity low density separating zone. This causes the low density debris in that zone to move from the debris receiving location rearwardly to be discharged at the rear discharge opening. The high density debris that is delivered to the receiving location descends through the upper high velocity low density separation zone toward the lower level of the water containing region.
The drum is rotated to cause the conveying structure to move the high density debris at the lower part of the water containing chamber region to a forward end of the drum. Then the high density debris is discharged through the front opening.
In a preferred form, there is a water discharge region at the water discharge location extending across the upper level of the water containing chamber region. The method further comprises discharging the additional water only at a portion of the water discharge region so that the additional water creates with the surrounding water a turbulent downstream flow. Desirably, this is accomplished by discharging the water through a plurality of nozzles to form a plurality of water jets. These nozzles are positioned in the preferred form on both sides of a center location of the water discharge region. As a further region, there is at least one discharge nozzle at a location beneath the water discharge region to direct a flow of water in a rearward direction.
The preferred configuration of the nozzles is that each nozzle has an elongate nozzle opening with a width dimension greater than its depth dimension, and with an elongate axis of each of said discharge openings being generally horizontally aligned. This results in high velocity flow patterns which expand laterally at a greater rate than vertical expansion.
In the preferred form, the water is discharged through the nozzles at a velocity of at least one foot per second, more desirably at least four feet per second, and also desirably at a velocity of at least ten feet per second. In a preferred embodiment the range is between ten to fifteen feet per second. It is to be understood that the velocity within the broader scope could be at 2, 3, 5, 7, 8, and 9 feet per second. Further the velocity could be increased by one flow per second increments up to fifteen feet per second which would be a preferred velocity, and through one foot per second velocity increments up to 20 or 25 feet per second. Desirably, the rear discharge opening is defined by a generally circular perimeter rim and is generally centered on an axis of rotation of the drum. The water flowing out of the rear opening is over a curved rim segment, and the water is delivered at a sufficient flow rate so that the curved segment over which the water flows is at least thirty degrees. At a higher velocity, the segment over which the water flows is at least forty five degrees, and with yet higher velocity at least sixty degrees.
Desirably, the low density debris is moved by the water flow from the debris receiving location into a predischarge zone section which is defined by an inwardly and upwardly tapering rear end wall leading to the rear discharge opening and through which the water accelerates to be discharged through the rear discharge opening. Desirably the rear edge portion of the rear end wall is aligned with the circular perimeter rim of the opening. This rear end wall is desirably configured approximately in a fursto-conical configuration.
The water and load density debris are discharged from the rear opening onto a low density debris receiving discharge structure having flow through openings through which the water falls to separate the low density debris from the water. Desirably, this low density debris receiving discharge structure comprises a surrounding fursto-conical side wall member with a smaller inlet opening and a larger outlet opening. This low density debris receiving discharge structure is rotated to tumble the low density debris to facilitate discharge of the same. Desirably this discharge structure is connected to the drum so as to be rotatable therewith.
Water and high density debris are discharged from the rear opening onto a high density debris receiving discharge structure having flow through openings through which the water falls to separate the high density debris from the water. This high density debris receiving discharge structure comprises a surrounding a fursto-conical side wall member with a smaller inlet opening and a larger outlet opening which is rotated to tumble a low density debris to facilitate discharge of the same, and which is desirably connected to the drums so as to be rotatable therewith.
The high density debris is discharge by rotating a discharge structure to engage the high density debris at the forward end of the drum and carry such high density debris to be discharged through the front discharge opening. Desirably the discharge structure is mounted to the drum so as to be caused to rotate by rotation of the drum. Further, in the preferred form, the discharge structure comprises a plurality of paddles which are circumferentially spaced and which engage the high density debris at a lower location to carry it to a higher location and cause discharge of the high density debris through the front discharge opening.
The high density conveying structure is positioned at an inside surface of the drum and extends radially inwardly therefrom with a rearward to forward slanting surface portion which engages the high density debris to cause forward movement of the high density debris.
The apparatus of the present invention has in large part been described in the above text relating to the method of the present invention. Thus, as indicated above, the apparatus comprises a rotatably mounted drum having the surrounding side walls, the front and rear end walls with the front and rear discharge openings, and also the high density conveying structure. There is support and drive section to support and rotate the drum.
There is a debris delivering section to deliver the debris into the processing chamber at a receiving location at the water containing chamber region. In a preferred form, this debris delivering section comprises a conveyor extending through one of the front and rear openings in the drum (desirably extending through the rear opening), and a hopper delivering the debris onto the rear end of the conveyor which then carries it inwardly above the water level in the processing chamber to deposit the debris off the front of the conveyor and onto the surface of the water at the receiving location.
There is also a water supply and delivery section which discharges water through the aforementioned nozzles (in the preferred form). In the overall system, there is a pair of settling tanks, and water is drawn from the settling tanks by a pump which in turn directs the water through a control valve and thence through a conduit section that extends through one of the front and rear openings in the drum. The conduits are desirably supported from the conveyor. The conduits extend outwardly to the water level and then terminate in rearwardly directed water nozzles.
Most all of the processing water is discharged through the rear opening along with the low density debris. The water discharged from both the rear and the front opening is collected in a tank positioned beneath the drum, and it is directed from this tank to the settling tanks where sludge and small particles settle out.
Other features and components of the present invention are described in the prior text under xe2x80x9cSummary of the Inventionxe2x80x9d and also are described in more detail in the full text that follows.